1JZ --> MK3 Swap Wiring Harness Routing

[Heggy]

JZA70 1JZ into '87 NA

Looking for experienced feedback on which method is better. The extend or reroute.

Option 1 : Extend main harness 18" and rewire JZ harness plugs to MA 70

Option 2: Drill 2.5 " hole in firewall below speedo cable (flat spot) reroute harness over AC and to reversed ECU. Rewire and extend body connectors (MA70 plugs).

Option 3: ???????

This is where I am in my swap. I swapped the JZ fuse box over and installed the wiring for ALT and Hyd fan sensor. I still have a couple of things to do for the AC compressor wiring.

I'm sure there are some that have done this, and I would like to know the best option

Thanks for any feedback

Cheers

 

[motorider9911]

Another option is to order a harness from Tweaked Performance. They will make you a new harness and you either have to send in your 7M harness ahead of time to avoid the 300 core charge, or wait till you get the harness and send it in 30 days after for a refund of the 300. Personally from doing over 8 builds with 8 different engines in 240's this is the route to go. Yes it is expensive however you have a known good harness, with properly assembled joints.

 

[Heggy]

Don't have $1200 burning a hole in my pocket at the moment.

 

[Heggy]

Well took a look today and decided to extend the JZ harness. There is very little room to route the harness behind the dash and if not routed properly it would likely be too short to comfortably mate with the ECU, not to mention modifying the ECU mount to fit it backwards. Went out and bought heat shrink and will start tomorrow....

I have the old 7M harness (and a bunch of wiring from the JZ clip) I will use for the extension so it should not be that bad.

 

[slapsticksammy]

Can you take some photos when this is done?

 

[Heggy]

Here are some pics that I took during assy. There is a lot of soldering but it is really an easy job to do. I used solder and heat shrink tubing for most of the connections and had to use some wire splices for the 10 gauge wires as I prefer that over soldering this big of a wire.

I have now completed all ECU plugs and the hydo fan plug, most of B1 (except for an AC wire, VSV and a Theft protection wire) and will start on M1 today as soon as I complete my assessment of the new connections on my cluster. My car was an N/A so no boost gauge. I wanted to keep things stock as much as possible. I ordered a boost gauge and electronics block off of ebay (the JZ cluster has them but are exact opposites to what I need) should be here on Thursday. Will also wire in the oil press idiot light on the JZ tach as I will remove the oil press gauge in favor of the boost gauge.

I also swapped the JZ Engine compartment fuse box so I could use the stock wiring for the alternator, EA2 and the rad sensor for the hydro fan. Unfortunately due to this swap I have to figure out an alternate for the power that went thru C1 to the Theft protection horn and I'm a little confused with the AC wiring as I also will keep the JZ AC compressor.

That's it for now, I will take some more pics today. I plan to leave the harness un-taped until after the engine is in the car to do some wiring checks and make sure all the connectors mate.

I tried to upload photos and it takes forever. I guess files are too big (2 meg) I will have to convert them to send or find a website to post...

 

[Heggy]

https://www.flickr.com/photos/125825544@N06/#

 

[motorider9911]

I understand not having the 1200 for a harness, I only did because of selling my previous DD and getting the MK3 real cheap. However it is nice to have a brand new harness not having to worry about old wire, or connections.

Nice Job! how many hours did it take?

 

[slapsticksammy]

I will be embarking on something similar soon. I thought about using MIL-spec amphenol connectors but I can't seem to find ones that a cheaply priced.

 

[Heggy]

The extension took about 20 hours. I also did the fuse box swap which only took about 6. Still don't know how to hook up AC yet as there are a number of differences in the circuits and I kept the JZ A/C pump. I only need to modify 1 line as the other one came from the clip.